Silent infarction as a risk factor for overt stroke in children with sickle cell anemia: a report from the Cooperative Study of Sickle Cell Disease.

OBJECTIVE: To determine whether children with homozygous sickle cell anemia (SCD) who have silent infarcts on magnetic resonance imaging (MRI) of the brain are at increased risk for overt stroke. METHODS: We selected patients with homozygous SCD who (1) enrolled in the Cooperative Study of Sickle Cell Disease (CSSCD) before age 6 months, (2) had at least 1 study-mandated brain MRI at age 6 years or older, and (3) had no overt stroke before a first MRI. MRI results and clinical and laboratory parameters were tested as predictors of stroke. RESULTS: Among 248 eligible patients, mean age at first MRI was 8.3 +/- 1.9 years, and mean follow-up after baseline MRI was 5.2 +/- 2.2 years. Five (8.1%) of 62 patients with silent infarct had strokes compared with 1 (0.5%) of 186 patients without prior silent infarct; incidence per 100 patient-years of follow-up was increased 14-fold (1.45 per 100 patient-years vs 0.11 per 100 patient-years, P =.006). Of several clinical and laboratory parameters examined, silent infarct was the strongest independent predictor of stroke (hazard ratio = 7.2, P =.027). CONCLUSIONS: Silent infarct identified at age 6 years or older is associated with increased stroke risk.

Sickle cell disease in childhood: Part II. Diagnosis and treatment of major complications and recent advances in treatment.

Treatment advances over the past 25 years have significantly decreased morbidity and mortality in children with sickle cell disease. Aggressive management of fever, early diagnosis of acute chest syndrome, judicious use of transfusions and proper treatment of pain can improve quality of life and prognosis for these children. Prophylactic hydroxyurea therapy has been shown to reduce the incidence and severity of pain crises in adults with sickle cell disease and has been effective in limited studies conducted in children. Research into stem cell transplantation provides hope that a cure for sickle cell disease may be possible.

Sickle cell disease in childhood: Part I. Laboratory diagnosis, pathophysiology and health maintenance.

Over the past 25 years, morbidity and mortality have decreased significantly in children with sickle cell disease, and screening tests are now available to diagnose the disease in newborns. The incidence of sepsis caused by pneumococcal and Haemophilus influenzae infections has declined because of the prophylactic administration of penicillin soon after birth and the timely administration of pneumococcal and H. influenzae type b vaccines. Optimal nutrition can maximize growth in children with sickle cell disease, and timely screening can identify complications such as retinal damage and chronic renal involvement, thereby ensuring prompt treatment. Family physicians and parents who have been educated about sickle cell disease can detect acute, life-threatening complications such as splenic sequestration crisis and acute chest syndrome at their onset, thereby allowing treatment to be instituted without delay.

Prediction of adverse outcomes in children with sickle cell disease.

BACKGROUND: The ability to identify infants with sickle cell anemia who are likely to have severe complications later in life would permit accurate prognostication and tailoring of therapy to match disease-related risks and facilitate planning of clinical trials. We attempted to define the features of such babies by following the clinical course of 392 children with sickle cell disease from infancy to about the age of 10 years. METHODS: We analyzed the records of 392 infants who received the diagnosis of homozygous sickle cell anemia or sickle cell-Beta(0)-thalassemia before the age of six months and for whom comprehensive clinical and laboratory data were recorded prospectively; data were available for a mean (+/-SD) of 10.0+/-4.8 years. Results obtained before the age of two years were evaluated to determine whether they predicted the outcome later in life. RESULTS: Of the 392 infants in the cohort, 70 (18 percent) subsequently had an adverse outcome, defined as death (18 patients [26 percent]), stroke (25 [36 percent]) frequent pain (17 [24 percent]), or recurrent acute chest syndrome (10 [14 percent]). Using multivariate analysis, we found three statistically significant predictors of an adverse outcome: an episode of dactylitis before the age of one year (relative risk of an adverse outcome, 2.55; 95 percent confidence interval, 1.39 to 4.67), a hemoglobin level of less than 7 g per deciliter (relative risk, 2.47; 95 percent confidence interval, 1.14 to 5.33), and leukocytosis in the absence of infection (relative risk, 1.80; 95 percent confidence interval, 1.05 to 3.09). CONCLUSIONS: Three easily identifiable manifestations of sickle cell disease that may appear in the first two years of life (dactylitis, severe anemia, and leukocytosis) can help to predict the possibility of severe sickle cell disease later in life.

Silent cerebral infarcts in sickle cell anemia: a risk factor analysis. The Cooperative Study of Sickle Cell Disease.

BACKGROUND: Silent infarcts have been reported in 17% of young patients with sickle cell disease and are associated with impaired performance on standardized psychometric tests. Risk factors for the development of these lesions have not been identified. METHODS: Investigators in the Cooperative Study of Sickle Cell Disease performed a brain magnetic resonance imaging scan on sickle cell anemia patients age 5.9 years and older who had been followed according to the protocols of the Cooperative Study since birth. Individuals with a known history of cerebrovascular accident were excluded from this analysis. Patients with and without silent infarctions were compared with regard to clinical and laboratory parameters. RESULTS: The study sample included 42 patients (18.3%) with silent infarcts. Patients who had silent infarcts were significantly more likely to have a clinical history of seizure and a lower painful event rate. Lower hemoglobin level, increased leukocyte count, elevated pocked red blood cell count, and SEN betaS globin gene haplotype were associated also with the presence of silent infarcts. There was no relationship between silent infarcts and platelet count, fetal hemoglobin level, reticulocyte percentage, serum aspartate aminotransferase level, total bilirubin concentration, blood pressure, growth parameters, or presence of alpha-thalassemia. A multivariate model for silent infarction identified the following as risk factors: low pain event rate, history of seizure, leukocyte count >/=11.8 x 10(9)/L, and the SEN betaS globin gene haplotype. CONCLUSIONS: Patients with risk factors for silent infarcts should be evaluated for cerebrovascular disease. If evidence of infarction is found, consideration must be given to therapeutic intervention. At present, the appropriate treatment has not been determined.

Cerebrovascular accidents in sickle cell disease: rates and risk factors.

Cerebrovascular accident (CVA) is a major complication of sickle cell disease. The incidence and mortality of and risk factors for CVA in sickle cell disease patients in the United States have been reported only in small patient samples. The Cooperative Study of Sickle Cell Disease collected clinical data on 4,082 sickle cell disease patients enrolled from 1978 to 1988. Patients were followed for an average of 5.2 +/- 2.0 years. Age-specific prevalence and incidence rates of CVA in patients with the common genotypes of sickle cell disease were determined, and the effects of hematologic and clinical events on the risk of CVA were analyzed. The highest rates of prevalence of CVA (4.01%) and incidence (0.61 per 100 patient-years) were in sickle cell anemia (SS) patients, but CVA occurred in all common genotypes. The incidence of infarctive CVA was lowest in SS patients 20 to 29 years of age and higher in children and older patients. Conversely, the incidence of hemorrhagic stroke in SS patients was highest among patients aged 20 to 29 years. Across all ages the mortality rate was 26% in the 2 weeks after hemorrhagic stroke. No deaths occurred after infarctive stroke. Risk factors for infarctive stroke included prior transient ischemic attack, low steady-state hemoglobin concentration and rate of and recent episode of acute chest syndrome, and elevated systolic blood pressure. Hemorrhagic stroke was associated with low steady-state hemoglobin and high leukocyte count.

Serotype-specific immunoglobulin G antibody responses to pneumococcal polysaccharide vaccine in children with sickle cell anemia: effects of continued penicillin prophylaxis.

OBJECTIVES: (1) To determine serotype-specific IgG antibody responses to reimmunization with pneumococcal polysaccharide vaccine at age 5 years in children with sickle cell anemia and (2) to determine whether continued penicillin prophylaxis had any adverse effects on these responses. STUDY DESIGN: Children with sickle cell anemia, who had been treated with prophylactic penicillin for at least 2 years before their fifth birthday, were randomly selected at age 5 years to continue penicillin prophylaxis or to receive placebo treatment. These children had been immunized once or twice in early childhood with pneumococcal polysaccharide vaccine and were reimmunized at the time of randomization. RESULTS: Serotype-specific IgG antibody responses to reimmunization varied according to pneumococcal serotype but in general were mediocre or poor; the poorest response was to serotype 6B. The antibody responses were similar in subjects with continued penicillin prophylaxis or placebo treatment, and in subjects who received one or two pneumococcal vaccinations before reimmunization. The occurrence of pneumococcal bacteremia was associated with low IgG antibody concentrations to the infecting serotype. CONCLUSIONS: Reimmunization of children with sickle cell anemia who received pneumococcal polysaccharide vaccine at age 5 years induces limited production of serotype-specific IgG antibodies, regardless of previous pneumococcal vaccine history. Continued penicillin prophylaxis does not interfere with serotype-specific IgG antibody responses to reimmunization.

Functional asplenia in hemoglobin SC disease.

The incidence of functional asplenia in sickle-hemoglobin C (SC) disease has not been defined, and the use of prophylactic penicillin to prevent life-threatening septicemia in this disorder is controversial. The percentage of red blood cells with pits (pit count) is a reliable assay of splenic function in other disorders but has not been validated in hemoglobin SC disease. To address these issues, we conducted a prospective, multicenter study of splenic function in persons with hemoglobin SC disease. Baseline clinical data were recorded, and red blood cell pit counts were performed on 201 subjects, aged 6 months to 90 years, with hemoglobin SC; 43 subjects underwent radionuclide liver-spleen scanning. Pit counts greater than 20% were associated with functional asplenia as assessed by liver-spleen scan, whereas pit counts less than 20% were found in subjects with preserved splenic function. Pit counts greater than 20% were present in 0 of 59 subjects (0%) less than 4 years of age, in 19 of 86 subjects (22%) 4 to 12 years of age, and in 25 of 56 subjects (45%) greater than 12 years of age. Other subjects with hemoglobin SC, who had previously undergone surgical splenectomy, had higher pit counts (59.7% +/- 9.5%) than splenectomized subjects without hemoglobinopathy (38.5% +/- 8.8%) or with sickle cell anemia (20.5% +/- 1.9%; P < .001). Two subjects with hemoglobin SC disease (not splenectomized), ages 14 and 15 years, with pit counts of 40.3% and 41.7% died from pneumococcal septicemia. These data indicate that functional asplenia occurs in many patients with hemoglobin SC disease, but its development is usually delayed until after 4 years of age. The pit count is a reliable measure of splenic function in hemoglobin SC disease, but values indicative of functional asplenia (> 20% in our laboratory) are higher than in other disorders. The routine administration of prophylactic penicillin to infants and young children with hemoglobin SC disease may not be necessary.

Accelerated healing of chronic sickle-cell leg ulcers treated with RGD peptide matrix. RGD Study Group.

Leg ulcers are a chronic manifestation of sickle-cell disease (SCD) and are often painful, disabling, and difficult to treat. RGD peptide matrix treatment is a novel therapy designed to provide a topical synthetic extracellular matrix that can act as a temporary substitute for the damaged natural matrix at the ulcer site. In this randomized, placebo-controlled, double-blind, prospective, multicenter investigation, SCD patients with full-thickness leg ulcers were treated with standard therapy plus RGD peptide matrix or saline placebo once weekly for up to 10 weeks. Healing in patients with chronic ulcers (2 months or greater in duration) was significantly accelerated (P = .0085) in RGD peptide matrix recipients compared with the placebo group. In these chronic ulcer cases, the average percent ulcer closure (decrease in ulcer surface area) in the RGD peptide matrix group (54.4% +/- 8.9%) exceeded that in the placebo group (19.0% +/- 24.3%) nearly threefold by study endpoint. Furthermore, RGD peptide matrix was equally effective in promoting healing of long persistent ulcers and ulcers of shorter duration. In contrast, standard therapy plus placebo was significantly less effective (P = .001) in promoting healing for ulcers of progressively greater duration. The results of this study provide preliminary evidence that RGD peptide matrix treatment may significantly accelerate healing of chronic sickle-cell leg ulcers.

Febrile episodes in children with sickle cell disease treated on an ambulatory basis.

Children with sickle cell disease have a greatly increased potential for developing rapid and at times fatal sepsis from Streptococcus pneumoniae. Hospitalization and parenteral antibiotic treatment in all febrile children with sickle cell disease have thus become the standard of care at most sickle cell centers. As an alternative approach, we managed selected febrile children with sickle cell disease on an ambulatory basis with parenteral ceftriaxone to determine its safety and effectiveness in preventing sepsis and reducing the number of days of hospitalization. Twenty of 40 children who presented with significant fever met the study criteria and received ceftriaxone on an ambulatory basis. Three were subsequently hospitalized. Compared with a previous year, when all febrile children were admitted, ceftriaxone use reduced the days of hospitalization from 214 (6.3 +/- 1.6 days/patient) to 111 days (2.8 +/- 0.7 days/patient). The empiric use of ceftriaxone appears safe and effective, but it requires an expanded study over an extended period.

Management of acute splenic sequestration crisis in sickle cell disease.

Acute splenic sequestration crisis (ASSC) is a significant cause of early morbidity in children with sickle cell disease. With timely diagnosis and prompt transfusion, the outcome is good. However, recurrences are frequent, and both splenectomy and long-term transfusion therapy have been advanced as appropriate preventive approaches. We describe the diagnosis, management, and course of 15 patients with ASSC followed at the St. Luke's-Roosevelt Hospital Center Comprehensive Sickle Cell Program. Based on our experience, we recommend surgery after the first episode of ASSC in the child 5 years of age and older and the choice of a year or more of long-term transfusion therapy for the child under 3. With intensive education of the parents, and with close observation and individualized management of the patient, the overall prognosis may be improved.

Spleen dysfunction in hemoglobinopathies determined by pitted red cells.

Splenic dysfunction measured by pitted red cells (pit) was studied in hemoglobinopathies (SS-, SC-, and S beta-type thalassemias and CC-type hemoglobinopathy) in relation to age, in steady state, and during certain significant events. Our experience revealed that the pit count rose with age during steady state in most children with SS disease. A marked increase in pit count was noted in patients with CC disease. The pit count in four patients with S beta+ thalassemia remained normal (i.e., less than 3.5%) at all ages. In children with homozygous SS disease tested at the time of pneumococcal sepsis, the pit count was universally elevated. The pit count was in the normal range in one child with SS disease and osteomyelitis but was elevated in all others. All children had normal pit counts (less than 3.5%) at the onset of acute splenic sequestration crisis, and the counts remained normal during transfusion therapy. No correlation was detected between the pit count and the size of the spleen in patients under 1 year of age.

Reversibility of splenic function by transfusion in two young adults with sickle cell anemia.

A level of circulating "pitted" or vesiculated red blood cells higher than 3.5% was recently reported in studies in the Cooperative Study of Sickle Cell Disease to correlate with splenic dysfunction as shown by spleen scans. Reversal of splenic dysfunction by transfusion in children with sickle cell anemia (SS disease) is known to occur in the young child. We report two older patients with homozygous sickle cell disease, aged 17 and 21 years, whose spleen function, as measured by pit count, was restored to normal range after transfusion.

Growth hormone response to growth hormone releasing factor in sickle cell disease.

Many children with sickle cell disease (SCD) have impaired growth during childhood and adolescence, with patterns of growth consistent with constitutional delay in growth and pubertal development (CDGD). We evaluated the growth hormone (GH) response to a rapid intravenous (i.v.) infusion of growth hormone releasing factor (GRF, 1-44, 1 microgram/kg) in six children with SCD whose growth patterns and bone ages were consistent with CDGD. The peak GH response of the SCD patients to GRF (29.2 +/- 14.3 ng/ml, mean +/- SD, n = 6) was not statistically significantly different from the peak GH response of the control children (29.0 +/- 6.3 ng/ml, mean +/- SD, n = 7). These findings suggest that pituicyte GH response to GRF is intact and is not the cause of the observed impaired growth in patients with SCD.

Pitfalls in diagnosis of osteomyelitis in children with sickle cell disease.

The cases of three children with unusual features of osteomyelitis and sickle cell disease are presented. Two children had salmonella osteomyelitis, one with a recurrence 1.5 years after adequate intravenous therapy. In the second, the bone scan was negative despite verified disease. The causative organism in the third case was Staphylococcus aureus, and there was extensive bone involvement of the radius without symptoms, but with a positive bone scan. It is recommended that the possibility of osteomyelitis be entertained in a child with sickle cell disease whenever there are symptoms and/or objective findings referrable to bone. Radionuclide scans, when used in timely fashion, can assist in the diagnosis, but confirmation can best be achieved by the recovery of microorganisms through blood culture and/or bone aspirate. The choice, dosage, and duration of antibiotic therapy should be determined by causative organisms and by serologic titers.

Problems and complications in the adolescent with sickle cell disease.

The period of adolescence in the patient with sickle cell disease seems to be a period of relative calm, medically speaking. The current 5-year prospective Cooperative Study of the Clinical Course of Sickle Cell Disease should demonstrate the actual spectrum of disease in this age group. The recent literature documents with significant relationship between retardation of growth and sexual maturation in the child with sickle cell disease, an effect which seems independent of the severity of the disease. Several other major problems in the adolescent are discussed, including psychological disturbances, leg ulcers, aseptic necrosis, pulmonary disease, priapism, stroke, cholelithiasis, and birth control. A retrospective series of 76 cases of sickle cell disease is briefly presented and the complication occurring during the second decade of life are reviewed.